Principal Engineer: Software Architecture & Modernization

abcfinancial; Poland; On-site; PLN 360,000 - 600,000; Full time

Job summary

ABC Fitness seeks a Principal Engineer to lead the architecture and hands-on modernization of critical software systems. You will shape the target architecture, migrate legacy code, and ensure compatibility and continuity while delivering tangible value.

You will stay close to implementation, working across Java/Springboot, Golang, Node/TypeScript backends, APIs, data access, and testing, turning risk into durable, scalable software with strong coding discipline.

Qualifications

• Substantial experience designing, building, operating, and evolving production backend systems, services, APIs, and distributed applications.
• Hands-on contributor with architectural influence and production focus.
• Proficiency in backend ecosystems such as Java/Springboot, Golang, Node/TypeScript.

Responsibilities

• Lead software architecture and modernization. Define target architecture, modules, and migration paths.
• Stay deeply hands-on in code with backend work and reviews.
• Design domain models and APIs with clear ownership and service contracts.
• Modernize foundations, upgrade frameworks and runtimes, and decompose code.
• Engineer for correctness, performance, and reliability across data access and messaging.
• Improve data access, persistence, and integration while preserving audit needs.
• Raise the bar for code quality and testing with strong review and validation.
• Create reusable engineering patterns and cross-team execution plans.
• Turn technical strategy into actionable, cross-team work with product and data teams.

Job description

ABC Fitness seeks a Principal Engineer to lead the architecture and hands-on modernization of critical software systems. You will shape the target architecture, migrate legacy code, and ensure compatibility and continuity while delivering tangible value.

You will stay close to implementation, working across Java/Springboot, Golang, Node/TypeScript backends, APIs, data access, and testing, turning risk into durable, scalable software with strong coding discipline.